The development of electronic computer and electronic communications technologies has been very mature. However, an electronic technology in which an electron is used as an information carrier is affected by a distribution latency effect, electromagnetic crosstalk, and the like. The development of the electronic technologies already meets a bottleneck, and already cannot satisfy requirements of current cloud computing or the like on a rate and communication quality of an electronic computer.
With the occurrence of monochromatic laser having high coherence, a photon having no electrical charge and distribution delay effect gradually replaces the electron and becomes an information carrier of optical communication. A photonic technology in which a photon is used as an information carrier can improve a transmission capacity, a processing speed, and a storage density of an information system. In view of the electronic computer and electronic communications technologies, a practical all-optical information system needs to be constituted by means of a fast optical switch device and optical interconnection between inside and outside of a chip. The development of such an integrated optical circuit is reflected in many aspects, such as an increase of a rate, expansion of a function, reliability and stability of a system, and compatibility with a micro-electronic system.
Considering a capability of being compatible with an existing mature micro-electronic processing technique, an integrated silicon photonic chip technology is a most potential solution for implementing functions, such as optical switching of a next generation all-optical communications network and optical interconnection between a data center and a central processing unit (CPU) of a computer. Nowadays, most optical switch nodes are implemented by using an optical add-drop multiplexer (OADM) and an optical cross-connect (OXC), and mainly depend on an optical fiber and a micro-electro-mechanical systems (MEMS) optical switch technology.
A conventional silicon photonic chip has a two-dimensional single-layer optical circuit, and a large optical energy loss caused by a waveguide intersection node in the chip limits a scale of the chip. Based on an idea of a printed circuit board (PCB) of a multi-layer circuit in an integrated circuit (IC) design, a three-dimensional photonic integrated circuit (3D-PIC) of a multi-layer integrated optical circuit is used, which can avoid the large loss caused by optical waveguide intersection. In addition, this three-dimensional photonic integrated circuit is more compact and efficient, which can increase a device density in the chip and a signal processing capability in a unit size, and also can reduce power consumption and costs.
In an electronic integrated circuit, interconnection between layers may be implemented by using a through-silicon via (TSV) technology in a multi-layer circuit board. Because of different performance of the photon and the electron, although a photonic integrated circuit may be laid out based on the electronic integrated circuit, optical signal exchange and sharing between different layers in the photonic integrated circuit cannot be implemented based on the TSV technology. That is, currently, optical signal exchange and sharing between different layers cannot be implemented in a multi-layer optical circuit.